1. Field of the Invention
The present invention relates to a display panel manufacturing method and a display device and particularly, to a display panel manufacturing method and a display device which are suitably applied to a plasma display for use in a flat type television, an information display device, or the like.
2. Description of the Prior Art
A plasma display device is a display device of such a type that ultraviolet rays are generated by gas discharge and phosphor is excited by the ultraviolet rays thus generated to emit light, thereby achieving a display, and it has been expected to be applied to a large-screen television, an information display device, or the like. Various systems have been developed for color plasma displays, and an AC surface discharge type plasma display device is excellent in brightness and easy manufacturing of panels among these systems.
FIG. 1 shows the conventional construction of a representative reflection type-AC surface discharge color plasma display panel.
The panel comprises back substrate 100 and front substrate 200. The back substrate 100 comprises glass substrate 1; belt-shaped data electrodes 2, bottom dielectric layer 3 and partition walls (bulkheads) 4, which are formed on the glass substrate 1; and red, green and blue phosphors 5 which are coated on the bottom portions and side surfaces of grooves formed between the partition walls 4. The front substrate 200 comprises glass substrate 6, and surface discharge electrodes 7, transparent dielectric layer 8 and protection layer 9 which are formed on the glass substrate 6. The front substrate 200 and the back substrate 100 are faced each other, and they are frit-sealed at the peripheral portion of the panel. The assembly thus frit-sealed is subjected to vacuum exhausting and heating, and then it is hermetically filled with gas, thereby completing the panel. The bottom dielectric layer 3 is not necessarily required, and the partition walls 4 and the phosphors 5 may be formed after the data electrodes 2 are formed.
As shown in FIG. 1, the typical partition walls 4 are designed in a stripe structure so that they extend vertically to the extension direction of the surface discharge electrodes 7 and in parallel to the extension direction of the data electrodes 2 and are arranged along the direction parallel to the extension direction of the data electrodes 2. The partition walls 4 serve to ensure the discharge space and also to prevent cross-talk of discharge and mixture of emitted light colors between adjacent cells, and they are important constituent elements for the plasma display panel.
In general, the partition walls 4 are designed at a height of about 100 to 150 xcexcm and at a width of about several tens xcexcm, and they may be formed by various forming methods. For example, there are practically used a method of repeating screen-printing and baking of dielectric paste for the partition walls 4 until the height of the dielectric paste thus screen-printed and baked is equal to a predetermined value; a method of coating and drying a dielectric paste of predetermined thickness, patterning the surface of the dielectric paste layer by using a photosensitive resist and then sandblasting the dielectric paste layer; and an additive method of forming a pattern of grooves on a photosensitive resist, coating and drying a paste for partition walls in the grooves and then removing the photosensitive resist.
However, in the case of the screen-printing method, it is difficult to keep high precision over the panel, because the precision of a screen plate is low and the plate itself is deformed. In addition, since the printing and drying operation must be repeated at about 10 times for example, it takes a long time to manufacture the partition walls 4, and the screen plate itself is severely wasted. Therefore, it is difficult to manufacture large-area and fine partition walls at a low cost. In the case of the sandblast method, although the manufacturing precision is high, because the patterning of the partition walls is performed by using a photography technique, the number of manufacturing steps is large and many materials are wasted, thus resulting in increase in manufacturing cost. In addition, it is relatively difficult to control the sectional shape of the partition walls. In the case of the additive method, the number of manufacturing steps is also large, which causes increase in manufacturing cost. In addition, it is difficult to manufacture high-aspect partition walls each having a narrow width.
Besides, there have been proposed methods of directly forming partition walls by using a mold unlike the above methods. For example, in Japanese Laid-open Patent Publication No. 9-134676, fluid partition wall member 11 composed of low melting-point glass, filler, binder, or the like is filled into recess portions for making partition wall portions formed in mold 20 by using a doctor blade method or the like (FIG. 2A). Substrate 10 is pressed against the mold 20 filled with the fluid partition wall member 11, and the fluid partition wall member 11 is hardened by heating or irradiation of ultraviolet rays to join the fluid partition wall member 11 and the substrate 10 into one body and then baked, thereby forming partition walls on the substrate 10 (FIG. 2B).
In Japanese Laid-open Patent Publication No. 9-283017, partition wall member 11 composed of low melting-point glass, filler, binder, solvent, or the like is coated on substrate 10 (FIG. 3A), and then mold 20 having recess portions formed therein is pressed against the substrate 10 coated with the partition wall member 11 to press-mold the partition wall member 11 in the recess portions of the mold 20 (FIG. 3B). After the mold 20 is separated, the partition wall member 11 is baked to form the partition walls on the substrate 10 (FIG. 3C). Further, As the other example, roll-shaped mold is used as the mold 20 and it is rolled on the substrate 10 coated with the partition wall member 11 to form partition wall-shaped partition wall member 11 on the substrate 10.
As to these methods using the mold, it is expected that the number of manufacturing steps is more reduced as compared wit the sandblast method, etc. and at least the shape of the partition wall member before the baking step can be obtained with the precision of the mold. However, industrial use of these methods has not yet been advanced at the present situation. That is, in practical use, the conventional methods using the molds have various disadvantages that much time is needed to cure the member filled in the mold, it is required to keep the substrate at high temperature while the substrate is brought into contact with the partition wall member and pressurized and it is impossible to perfectly separate the mold from the partition wall member, because the adhesion strength between the substrate and the partition wall portions cannot be sufficiently enhanced.
A display panel manufacturing method comprises: a step of sandwiching a plate-shaped partition wall-forming member between a mold having an inverted shape to partition walls and a counter (support) mold, and press-molding the partition wall-forming member to form a partition wall member comprising partition wall portions and a bottom insulating layer portion in close contact with the mold; and a step of transferring the partition wall member onto a display substrate.
A display device according to the present invention is manufactured by the display panel manufacturing method of the present invention.
The present invention is suitably applied to an AC discharge type plasma display device, however, it may be applied to various display devices using other partition walls. For example, it may be applied to display devices such as FED (Field Emission Display) for emitting electrons from a cold cathode electrode source to excite phosphor, PALC (Plasma address Liquid Crystal Display) for controlling liquid crystal by using a plasma switch, VFD (Vacuum Fluorescent Display) for exciting phosphor by using low-speed electron beams, or the like. Further, the present invention is not limited to the AC discharge type plasma display, but it may be applied to a DC (Direct Current) discharge type plasma display. In the case of the AC discharge type plasma display, the electrodes are covered by the bottom insulating layer. However, in the case of such a display device that the electrodes and the phosphor are exposed to the space, the electrodes and the phosphor may be formed on the bottom insulating layer.